Although some of the cellular mechanisms of neuronal injury after ischemic stroke are fairly well understood, the neuronal death after ischemic stroke cannot be well controlled because of a lack of efficient treatments. The long-term goal of my research is to develop an effective strategy for ischemic stroke therapy. The proposed research is focused on targeting the post- ischemic inflammation at blood-brain barrier (BBB) in search of new approaches for stroke therapy. We propose a novel RNA nanoparticle, 3WJ-pRNA/2siICAM-FB4, consisting of one RNA aptamer (FB4), two ICAM-1 siRNA and a 3-way junction of packaging RNA (3WJ-pRNA) of bacteriophage phi29. FB4 is a RNA aptamer specific to transferrin receptor (TfR) that can recognize TfRs at the BBB and facilitate RNA nanoparticle delivery into brain endothelial cells. Once the 3WJ-pRNA/2siICAM-FB4 enters the cell, the siRNAs will be released and knockdown ICAM-1 expression leading to inhibition of inflammatory responses at the BBB. The pRNA 3-way junction serves as the core for holding FB4 and siRNAs together without disrupting the folding of either of the attached payload. We will use mouse transient ischemic stroke model in vivo and oxygen-glucose deprivation in primary brain endothelial cells in vitro to demonstrate the feasibility of this vascular targeting strategy for treatment of ischemic stroke. Our central hypothesis is that the 3WJ-pRNA/2siICAM-FB4 has therapeutic effects on ischemic stroke by inhibition of post-ischemic inflammation. Specific Aims: Aim 1: Determine pharmacological activity of 3WJ-pRNA/2siICAM-FB4 in vitro. Aim 2: Evaluate protective effect of 3WJ- pRNA/2siICAM-FB4 in transient ischemic stroke model in vivo. This project will develop a novel brain-targeted RNA therapeutics for therapy of ischemic stroke, and this approach could be broadly applied for therapy of diseases affecting the BBB and the central nervous system (CNS).